The present invention relates to a method of preparing refractory fibers. More specifically, it relates to an improved method of preparing metal oxide fibers.
Energy conservation efforts by industry in recent years have led to a 20 percent annual growth rate (from 1976-1982) in the use of ceramic fibers for high temperature insulation applications. Furnace lining products fabricated from ceramic fibers have a much lower heat capacity and are much better insulators than traditionally used dense firebrick refractories. Hot face replacement of firebrick with a fibrous refractory lining can reduce thermal conductivity by more than 50 percent, and the lower heat capacity of the fibrous refractory lining reduces heat-up costs and allows faster heating/cooling cycle rates.
Currently available ceramic fiber refractory products, which are fabricated mainly from aluminosilicate or alumina fibers, cannot be used at temperatures above approximately 1600.degree. C. Products made from fibrous zirconia are useful at temperatures up to 2200.degree. C. but are too expensive for normal industrial furnace lining applications. The cost (1982) of bulk ceramic fibers, which increases significantly with maximum service temperature (mst), is $1-3/lb for typical aluminosilicates (1260.degree. C. mst), $5/lb for mixed aluminosilicate/Al.sub.2 O.sub.3 products (1480.degree. C. mst), $22/lb for Al.sub.2 O.sub.3 (1600.degree. C. mst), and $47/lb for ZrO.sub.2 (2200.degree. C. mst). The cost/performance data on currently available fibrous ceramic products indicates a need in the marketplace for a ceramic fiber material that can be used in the temperature range 1600.degree. C.-2200.degree. C. and sell at a price competitive with Al.sub.2 O.sub.3 fibers. MgO fibers (mp 2800.degree. C.) could be used at temperatures of at least 2200.degree. C. but could have a significantly lower raw material cost than either ZrO.sub.2 or Al.sub.2 O.sub.3 fibers.